MSE and Windows Defender uses the same Engine. You just need either one of them. You could use Windows Defender just run a manual scan. MSE and Malwarebtyes are good configuration.
Hope this helps,
Try a clean boot to determine the problem of being slow.
Get Malwarebytes, Microsoft Security Essentials and the Windows Firewall.
Perform a clean startup to determine whether background programs are interfering with your game or program